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97 Jeep Cherokee - No Spark

I have a 97 cherokee 4.0L Auto, with just 68K miles. In three years all I have had to do is basic servicing. I have had zero faults. Last weekend it would not start (no spark or fuel being injected), and a friend towed me home. I have since spent several hours on the web to try and find a fix. I have read all about the CPS and the cam sensor in the distributor, plus checking the fuel pump etc.

So far I have established there is fuel under pressure in the fuel rail by pressing the pin on the valve, I checked all fuses and swapped around the relays, and I have disconnected and reconnected the battery after giving it a full charge. The earth strap from the cyl head to bulkhead is in good order. I have disconnected and reconnected the CPS several times.

The instruments and warning lights are behaving as normal. i.e. The warning lights come on when the ignition is switched on and then go out after a few seconds. The check engine light comes on then goes off with the others.

I then ran the diagnostics by holding down the trip meter button and turning on the ignition. It ran through the numbers from 000000 to

999999 and then went back to 0.000. It did not come up with any faults or a 55 to say the test was complete. I then tried the test with CPS disconnected and still got no fault showing. Whilst indexing through 000000 111111 222222 etc., all the gauges seemed to go through a sequence increasing in value and then decreasing back to zero.

So the diagnostics do not indicate a problem or even show that the battery has been disconneted recently.... But I still have no spark or fuel. Any ideas or suggestions. thanks in advance

Bob Turner

Reply to
bob.turner
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Bob,

Since no one's jumped into the quagmire just yet, let me remind you that code retrieval is on-off-on-off-on within 5 [?] seconds, not the instrument cluster test you're performing. While we're at it, your CPS may not trip a code simply unplugged unless you're cranking. Your logic, to the best of my knowledge, is headed in the right direction with the no spark, no injector symptom.

There -- step one.

J> I have a 97 cherokee 4.0L Auto, with just 68K miles. In three years all

Reply to
Jon

I'll jump in too. I would recommend you get a manual for it, even a Cheapie Haynes gives the multimeter tests for the coil and some for the ignition module to see if they are still good.

Maybe you can find the manual online, I know a few are...

I don't know if you can retrieve codes in a 97 or not, but it is key on, off, on, off, on within a few seconds if it works.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > I have a 97 cherokee 4.0L Auto, with just 68K miles. In three years all
Reply to
Mike Romain

Reply to
L.W. (Bill) Hughes III

I agree, if it is bad, there wll be no spark. There is no ggod way to check it for sure unless you have a scope to see pulses from it. As long as coil is not open to set a code it can still be bad and still read resestance on a test. It is its ability to send pulses that makes it or breaks it.

----------------- TheSnoMan.com

Reply to
SnoMan

Maybe go to Autozone and get them to read the codes with their hand held unit. They do this for free. Tomes

Reply to
Tomes

Hi

thanks for the responses, I have tried the on-off-on-off-on, and on-off-on-off-on-off-on, both within five seconds, and also by waiting for the odometer to light at each on. Still no codes.

Unfortunately I am 2 hours from a dealer in the back of beyond, and no faith in local shops. Can anyone help with an OEM part No. for both the crank and cam postion sensor, as I will order both parts.

thanks

snipped-for-privacy@clix.pt wrote:

Reply to
bob.turner

Man I hate shotgunning parts at things...

Do you have a multimeter? If so I would check for power at the coil positive with the key in 'run'. If I had power there, I would unplug the coil and check it with the meter. Ok, my Haynes covers the 97 and it says from the coil + to the coil case should be an open circuit or infinite resistance. If you touch the positive and negative with the meter, it should read close to 0 or continuity. Then check the resistance from the negative lead to the high voltage one. It should 'not' read infinite or open, but show 'some' resistance on the high ohm scale. (whatever 'some' means?)

If no power to the coil with the key in run, I then go after the starter relay connections on the fender by the battery. If the colors are the same, the green wire is the one to check.

I know my multimeter can read the pulses to the negative side of the coil when set on volts or you can use a test light to check for pulses when the engine is cranking over. If no pulses think CPS or even ignition module.

I also know my meter will read the pulses coming out of the CPS and distributor if I back feed the probe into the plug.

One other 'gotcha' on the newer ones is the battery. If the battery has a bad cell, it can still crank over the engine, but it won't have enough 'volts' to fire up the computer parts. I would recommend you put a multimeter on the posts and read it when cranking over. If you have less than 10.5 V I think it is, it won't fire up. I believe it will go under that with a bad cell.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > Hi
Reply to
Mike Romain

Let's try something simple and free. Just reseat the plug for the CPS! A dirty connection will keep it from working. It's round and is on the left rear of the engine. One end disappears down to the bellhousing area.

JoBo

Reply to
Jo Bo

Reply to
L.W. (Bill) Hughes III

Reply to
philthy

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